U.S. patent number 6,647,292 [Application Number 09/663,606] was granted by the patent office on 2003-11-11 for unitary subcutaneous only implantable cardioverter-defibrillator and optional pacer.
This patent grant is currently assigned to Cameron Health. Invention is credited to Gust H. Bardy, Riccardo Cappato.
United States Patent |
6,647,292 |
Bardy , et al. |
November 11, 2003 |
**Please see images for:
( Certificate of Correction ) ** |
Unitary subcutaneous only implantable cardioverter-defibrillator
and optional pacer
Abstract
A unitary subcutaneous implantable cardioverter-defibrillator is
disclosed which has a long thin housing in the shape of a patient's
rib. The housing contains a source of electrical energy, a
capacitor, and operational circuitry that senses the presence of
potentially fatal heart rhythms. Provided on the housing are
cardioversion/defibrillation electrodes located to deliver
electrical cardioversion-defibrillation energy when the operational
circuitry senses a potentially fatal heart rhythm. The unitary
subcutaneous implantable cardioverter-defibrillator does not have a
transvenous, intracardiac, epicardial, or subcutaneous
electrode.
Inventors: |
Bardy; Gust H. (Seatlle,
WA), Cappato; Riccardo (Ferrara, IT) |
Assignee: |
Cameron Health (SanClemente,
CA)
|
Family
ID: |
24662543 |
Appl.
No.: |
09/663,606 |
Filed: |
September 18, 2000 |
Current U.S.
Class: |
607/5; 607/119;
607/36; 607/4 |
Current CPC
Class: |
A61N
1/3906 (20130101); A61N 1/3956 (20130101); A61N
1/37512 (20170801); A61N 1/375 (20130101); A61N
1/39622 (20170801); A61N 1/3975 (20130101); A61N
1/3968 (20130101); A61N 1/3756 (20130101) |
Current International
Class: |
A61N
1/375 (20060101); A61N 1/39 (20060101); A61N
1/372 (20060101); A61N 001/39 () |
Field of
Search: |
;607/4,5,9,36,119 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0 517 494 |
|
Dec 1992 |
|
EP |
|
0 517 494 |
|
Dec 1992 |
|
EP |
|
0 517 494 |
|
Dec 1992 |
|
EP |
|
0 627 237 |
|
Dec 1994 |
|
EP |
|
WO 97/29802 |
|
Aug 1997 |
|
WO |
|
WO 97/29802 |
|
Aug 1997 |
|
WO |
|
WO 99/53991 |
|
Oct 1999 |
|
WO |
|
Other References
International Search Report dated Mar. 26, 2002, PCT/US01/29168
filed Sep. 14, 2001, published as WO 02/22208 on Mar. 21, 2002,
Subcutaneous Only Implantable Cardioverter Defibrlillator &
Optional Pacer, Inventors: Gust H Bardy et al. .
Written Opinion dated Sep. 10, 2002, PCT/US01/29168 filed Sep. 14,
2001, published as WO 02/22208 on Mar. 21, 2002, Subcutaneous Only
Implantable Cardioverter Defibrlillator & Optional Pacer,
Inventors: Gust H Bardy et al. .
International Search Report dated Mar. 21, 2002,, PCT/US01/29106
filed Sep. 14, 2001, published as WO 02/24275 on Mar. 28, 2002,
Unitary Subcutaneous Only Implantable Cardioverter Defibrillator
& Optional Pacer, Inventors: Gust H Bardy et al. .
Written Opinion dated Sep. 3, 2002, PCT/US01/29106 filed Sep. 14,
2001, published as WO 02/24275 on Mar. 28, 2002, Unitary
Subcutaneous Only Implantable Cardioverter Defibrillator &
Optional Pacer, Inventors: Gust H Bardy et al. .
Journal of the American Medical Association (JAMA), Vol 214, No 6,
1123pp, Nov. 9, 1970, "Completely Implanted Defibrillator", an
editorial comment by JC Schuder PhD. .
Amer Soc Trans Artif Int Organs, Vol XVI, 1970, 207-212pp,
"Experimental Ventricular Defibrillation With An Automatic &
Completely Implanted System", by JC Schuder PhD et al. .
Archives of Internal Medicine (Specialized Journal of the AMA), Vol
127, Feb. 1971, Letters to the Editor 317pp, "Standby Implanted
Defibrillators", an editirial comment by JC Schuder PhD. .
Journal of the American Medical Association (JAMA), Vol 213,
615-616pp, 1970, "Automatic Detection & Defibrillation of
Lethal Arrhythmias--A New Concept", by Mirkowski et al. .
IEEE Transactions on Bio-Medical Engineering, Vol BME-18, No 6,
Nov. 1971, 410-415pp, "Transthoracic Ventricular Defibrillation In
The Dog With Truncated and Untruncated Exponential Stimuli", by JC
Schuder PhD et al. .
Pace, Vol 16, Part I, Jan. 1993, 95-124pp, "The Role Of An
Engineering Oriented Medical Research Group In Developing Improved
Methods & Devices For Achieving Ventricular Defibrillation: The
University Of Missouri Experience", by JC Schuder PhD. .
Journal of Cardiovascular Electrophysiology, Vol 12, No 3, Mar.
2001, 356-360pp, Copyright 2001, by Future Publishing Company Inc,
Armonk-NY 1050-0418, "Nonthoracotomy Implantable Cardioverter
Defibrillator Placement In Children", by Rainer Gradaus MD et al.
.
Journal of Cardiovascular Electrophysiology, Vol 12, No 3, Mar.
2001, 361-362pp, Copyright 2001, by Future Publishing Company Inc,
Armonk-NY 1050-0418, "Implantable Defibrillators In Children: From
Whence to Shock", by Richard A Friedman MD et al..
|
Primary Examiner: Jastrzab; Jeffrey R.
Attorney, Agent or Firm: Gottlieb, Rackman & Reisman,
P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This patent application is related to U.S. patent application Ser.
No. 09/663,607, filed Sep. 18, 2000, pending, the disclosure of
which is incorporated by reference.
Claims
What is claimed is:
1. A unitary subcutaneous implantable cardioverter-defibrillator
comprising: a long thin housing with first and second ends that is
curved in a shape of a patient's rib wherein the housing contains a
source of electrical energy, a capacitor, and operational circuitry
that senses the presence of potentially fatal heart rhythms;
cardioversion/defibrillation electrodes located at the ends of the
housing; means for delivering electrical
cardioversion-defibrillation energy when the operational circuitry
senses a potentially fatal heart rhythm; and the absence of a
transvenous, intracardiac, or epicardial, electrode.
2. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the electrical cardioversion-defibrillating
energy is equal to or greater than 800 Volts.
3. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 2 wherein the electrical cardioversion-defibrillating
energy ranges from about 800 volts to about 2000 volts.
4. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the electrical cardioversion-defibrillating
energy ranges from about 40 Joules to about 150 Joules.
5. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 further comprising at least two sensing electrodes
located on the housing.
6. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 5 wherein the sensing electrodes are spaced apart by about
1 to about 10 cm.
7. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 6 wherein the first and second sensing electrodes are
spaced apart by about 4 cm.
8. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the operational circuitry can also sense the
presence of bradycardia rhythm.
9. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 8 further comprising means for delivering cardiac pacing
energy when the operational circuitry senses a bradycardia
rhythm.
10. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the operational circuitry is programmable.
11. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the operational circuitry can detect
tachycardia.
12. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 11 further comprising means for delivering antitachycardia
pacing when the operational circuitry senses a tachycardia
rhythm.
13. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 11 wherein the ventricular tachycardia detected is greater
than 240 beats per minute.
14. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the operational circuitry can detect atrial
tachycardia and atrial fibrillation.
15. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 14 wherein the operational circuitry can deliver
defibrillation energy to treat the detected atrial
fibrillation.
16. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the operational circuitry can induce ventricular
tachycardia or ventricular fibrillation.
17. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 16 wherein the ventricular tachycardia or ventricular
fibrillation is induced by shocks on the T wave.
18. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 16 wherein the ventricular tachycardia or ventricular
fibrillation is induced by low direct current voltage applied
during the entire cardiac cycle.
19. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the electrical cardioversion-defibrillating
energy is delivered in a biphasic wave form.
20. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the capacitance is about 50 to about 200 micro
farads.
21. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the housing is malleable.
22. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the housing is provided with at least one
sensing electrode.
23. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the housing is provided with one or more sensing
electrodes, and wherein said cardioverter-defibrillator is further
provided with a subcutaneous electrode with one or more sensing
electrodes, and means for selecting two sensing electrodes from the
sensing electrodes located on the housing and the sensing electrode
located on the subcutaneous electrode that provide adequate QRS
wave detection.
24. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the electrical cardioversion-defibrillating
energy is delivered for about 10 to about 20 milliseconds total
duration and with the initial positive phase containing
approximately 2/3 of the energy delivered.
25. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the operational circuitry comprises an impedance
detection for measuring the undulations in transthoracic impedance
created during respiration.
26. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 25 wherein the operational circuitry can also measure the
cardiac output using transthoracic impedance.
27. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 wherein the housing ranges in length from about 15 to
about 20 cm.
28. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 27 wherein the unitary subcutaneous implantable
cardioverter-defibrillator is provided in different incremental
sizes.
29. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 1 further comprising a plug-in core member inside the
housing of the unitary subcutaneous implantable
cardioverter-defibrillator wherein the plug-in core member contains
the source of electrical energy, the capacitor, and the operational
circuitry.
30. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 29 wherein the housing ranges in length from about 15 to
about 20 cm.
31. The unitary subcutaneous implantable cardioverter-defibrillator
of claim 29 wherein the unitary subcutaneous implantable
cardioverter-defibrillator is provided in different incremental
sizes.
32. A method of implanting a unitary implantable subcutaneous
cardioverter-defibrillator in a patient comprising the steps of;
making only one skin incision in the thoracic region of the
patient; inserting a curved introducer through the skin incision to
make a subcutaneous path in the thoracic region such that the path
terminates subcutaneously at an end location that if a straight
line were drawn from the skin incision to the end location, the
line would intersect the heart of the patient; implanting a unitary
subcutaneous cardioverter-defibrillator that has a long thin
housing that is curved in a shape of a patient's rib; and closing
the skin incision.
33. The method of implanting a subcutaneous
cardioverter-defibrillator of claim 32 further comprising the step
of injecting a local anesthetic through the curved introducer.
34. The method of implanting a subcutaneous
cardioverter-defibrillator of claim 32 wherein the skin incision is
located in the left anterior axillary line approximately at the
level of the patient's cardiac apex.
35. A unitary cardioverter-defibrillator for subcutaneous
implantation, comprising: a canister comprising a biocompatible
housing enclosing and containing cardioversion-defibrillation
circuitry, said housing having a downward taper continuously formed
along at least one exterior periphery of the biocompatible housing;
and a pair of electrodes formed on opposite ends of the
biocompatible housing and electrically interfaced to the
cardioversion-defibrillation circuitry to deliver an electrical
therapy to the heart of a patient.
36. A unitary cardioverter-defibrillator according to claim 35,
further comprising: at least one sensing electrode formed on, and
electrically insulated from, the biocompatible housing and
electrically interfaced to the cardioversion-defibrillation
circuitry.
37. A unitary cardioverter-defibrillator according to claim 35,
further comprising: at least one electrically insulated surface
defined on an outer surface of the biocompatible housing and
juxtaposed to the pair of electrodes.
38. A unitary cardioverter-defibrillator according to claim 37,
further comprising: at least one sensing electrode formed on the at
least one electrically insulated surface and electrically
interfaced to the cardioversion-defibrillation circuitry.
39. A unitary cardioverter-defibrillator according to claim 37,
further comprising: an insulated margin around at least one of the
pair of electrodes along the at least one electrically insulated
surface and defining a concentrated electrically conductive
surface.
40. A unitary cardioverter-defibrillator according to claim 37,
wherein the at least one electrically insulated surface is
constructed from at least one of a silicon, polyurethane, ceramic,
titanium-ceramic bonded, Parylene-coated, and other biocompatible
material.
41. A unitary cardioverter-defibrillator according to claim 35,
further comprising: monitoring circuitry integral to the
cardioversion-defibrillation circuitry and deriving physiological
measures relating to at least one of QRS signal morphology, QRS
signal frequency content, QRS R-R interval stability data, and QRS
amplitude characteristics.
42. A unitary cardioverter-defibrillator according to claim 35,
further comprising: a pulse generator integral to the
cardioversion-defibrillation circuitry and producing an
anti-arrhythmia waveform for anti-arrhythmia therapy via the pair
of electrodes responsive to the cardioversion-defibrillation
circuitry.
43. A unitary cardioverter-defibrillator according to claim 42,
further comprising: the pulse generator generating the
anti-arrhythmia waveform as a biphasic waveform with
characteristics comprising at least one of a capacitance between
approximately 50 .mu.F and 200 mF, voltage between approximately
800 V and 2000 V, energy between 40 J and 150 J, and a duration
between approximately 5 msec to 25 msec.
44. A unitary cardioverter-defibrillator according to claim 43,
further comprising: the cardioversion-defibrillation circuitry
initiating the anti-arrhythmia therapy upon a cardiac ventricular
rate of around 240 bpm sustained over an at least 4 second
interval.
45. A unitary cardioverter-defibrillator according to claim 43,
further comprising: the cardioversion-defibrillation circuitry
confirming the anti-arrhythmia therapy upon a cardiac ventricular
rate of around 240 bpm sustained over an approximately 1 second
interval.
46. A unitary cardioverter-defibrillator according to claim 43,
further comprising: the cardioversion-defibrillation circuitry
terminating the anti-arrhythmia therapy upon a cardiac ventricular
rate of around 240 bpm sustained over an at least 4 second
interval.
47. A unitary cardioverter-defibrillator according to claim 43,
further comprising: power supply components integral to the
cardioversion-defibrillation circuitry, consisting essentially of
four or more batteries and four or more capacitors and providing
power sufficient to generate the anti-arrhythmia waveform.
48. A unitary cardioverter-defibrillator according to claim 35,
further comprising: pacing circuitry operatively conjunctive to the
cardioversion-defibrillation circuitry which generates at least one
of an anti-bradycardia and an anti-tachycardia pacing waveform via
the pair of electrodes responsive to the
cardioversion-defibrillation circuitry.
49. A unitary cardioverter-defibrillator according to claim 35,
further comprising: induction circuitry integral to the
cardioversion-defibrillation circuitry which generates low
amplitude voltage on a T-wave of an ECG via the pair of electrodes
responsive to the cardioversion-defibrillation circuitry.
50. A unitary cardioverter-defibrillator according to claim 35,
further comprising: a pair of semi-converging tapers continuously
formed about opposite sides of the downward taper.
51. A unitary cardioverter-defibrillator according to claim 50,
further comprising: at least one surface of the biocompatible
housing formed in at least one of a curved and non-linear
surface.
52. A unitary cardioverter-defibrillator according to claim 51,
further comprising: the at least one surface formed as a radian
bend curving continuously approximately axial to the biocompatible
housing.
53. A unitary cardioverter-defibrillator according to claim 35,
further comprising: at least one of a fractalized and a wrinkled
surface formed on the outer surface of the biocompatible
housing.
54. A unitary cardioverter-defibrillator according to claim 35,
wherein the biocompatible housing is constructed from at least one
of a titanium alloy and another biocompatible material, such other
material being malleable.
55. A unitary cardioverter-defibrillator according to claim 35,
further comprising: monitoring circuitry integral to the
cardioversion-defibrillation circuitry and obtaining physiological
measures via the pair of electrodes.
56. A unitary cardioverter-defibrillator according to claim 35,
further comprising: each of the pair of electrodes formed
non-circumferentially on the biocompatible housing and with an
overall electrically active component of less than approximately 10
cm.sup.2.
57. A unitary cardioverter-defibrillator according to claim 35,
further comprising: each of the pair of electrodes interfacing with
high voltage and low impedance circuitry.
58. A unitary cardioverter-defibrillator according to claim 57,
further comprising: a plurality of sensing electrodes formed on the
biocompatible housing, each sensing electrode interfacing with low
voltage and high impedance circuitry.
59. A unitary cardioverter-defibrillator according to claim 58,
further comprising: each such sensing electrode formed on opposite
ends of the biocompatible housing.
60. A unitary cardioverter-defibrillator according to claim 58,
further comprising: each such sensing electrode formed between the
pair of electrodes.
61. A unitary cardioverter-defibrillator according to claim 58,
further comprising: at least one such sensing electrode formed
non-circumferentially on the biocompatible housing.
62. A unitary cardioverter-defibrillator for subcutaneous
implantation, comprising: a canister comprising a biocompatible
housing enclosing and containing cardioversion-defibrillation
circuitry; and a pair of electrodes formed on opposite ends of the
biocompatible housing and electrically interfaced to the
cardioversion-defibrillation circuitry to deliver an electrical
therapy to the heart of a patient; wherein said canister has two
ends, one end being a thicker end within which the
cardioversion-defibrillation circuitry is contained.
63. A unitary cardioverter-defibrillator according to claim 62,
further comprising: a core operational member containing the
cardioversion-defibrillation circuitry separate from the
biocompatible housing; and a hollow recess formed within the
biocompatible housing operationally disposed to receive the core
operational member.
64. A unitary cardioverter-defibrillator according to claim 63,
further comprising: a plurality of connectors matchingly formed on
a proximal end of the core operational member and on the distal end
of the hollow recess, each connector interfacing the
cardioversion-defibrillation circuitry to the pair of
electrodes.
65. A unitary cardioverter-defibrillator according to claim 63,
further comprising: an endcap with ribbed fittings formed along a
proximal end of the core operational member and hermetically
fitting within the hollow recess.
66. A unitary cardioverter-defibrillator for subcutaneous
implantation, comprising: a canister comprising a biocompatible
housing enclosing and containing cardioversion-defibrillation
circuitry; and a pair of electrodes formed on opposite ends of the
biocompatible housing and electrically interfaced to the
cardioversion-defibrillation circuitry to deliver an electrical
therapy to the heart of a patient; wherein the biocompatible
housing has one of several incremental sizes.
67. A unitary cardioverter-defibrillator for subcutaneous
implantation, comprising: a canister comprising a biocompatible
housing enclosing and containing cardioversion-defibrillation
circuitry; and a pair of electrodes formed on opposite ends of the
biocompatible housing and electrically interfaced to the
cardioversion-defibrillation circuitry to deliver an electrical
therapy to the heart of a patient; wherein the biocompatible
housing is shaped conformal to the rib cage.
68. A unitary cardioverter-defibrillator for subcutaneous
implantation, comprising: a canister comprising a biocompatible
housing enclosing and containing cardioversion-defibrillation
circuitry; and a pair of electrodes formed on opposite ends of the
biocompatible housing and electrically interfaced to the
cardioversion-defibrillation circuitry to deliver an electrical
therapy to the heart of a patient; wherein the biocompatible
housing is further formed conformal to at least one of the fourth,
fifth and sixth anterior rib spaces of a patient.
69. A unitary subcutaneous cardioverter-defibrillator with
electrically active canister for minimally invasive implantation,
comprising: a subcutaneously implantable canister comprising a
sterilizable biocompatible housing enclosing and containing
cardioversion-defibrillation circuitry interfaceable through the
biocompatible housing, the biocompatible housing formed into a
partially curved surface along a longitudinal axis, with a downward
taper continuously formed along an exterior periphery of the
biocompatible housing, and a pair of semi-converging tapers
continuously formed about opposite sides of the downward taper; and
a pair of electrodes formed on opposite and facing ends of the
biocompatible housing and electrically interfaced via one or more
internal conductors to the cardioversion-defibrillation circuitry
to deliver an electrical therapy to the heart of a patient
therebetween.
70. A unitary subcutaneous cardioverter-defibrillator according to
claim 69, further comprising: the pair of electrodes further
interfacing with sensing circuitry and providing a sensing function
to the cardioversion-defibrillation circuitry.
71. A unitary subcutaneous cardioverter-defibrillator according to
claim 69, further comprising: at least one of the pair of
electrodes formed as a concentrated electrically conductive surface
defined about a surface of the biocompatible housing and facing the
heart when implanted.
72. A unitary subcutaneous cardioverter-defibrillator according to
claim 69, further comprising at least one electrically insulated
surface defined about a surface of the biocompatible housing facing
away from the heart and juxtaposed to the pair of electrodes.
73. A unitary subcutaneous cardioverter-defibrillator according to
claim 72, further comprising: an insulating area substantially
interposed between the pair of electrodes and the at least one
electrically insulated surface.
74. A unitary subcutaneous cardioverter-defibrillator according to
claim 69, further comprising: at least one sensing electrode formed
on, and electrically insulated from, the pair of electrodes and
electrically interfaced to the cardioversion-defibrillation
circuitry, each sensing electrode interfacing with sensing
circuitry and providing a sensing function to the
cardioversion-defibrillation circuitry.
75. A unitary subcutaneous cardioverter-defibrillator according to
claim 74, further comprising: an electrically insulated surface
about each at least one sensing electrode abutting the
biocompatible housing and marginal to the pair of electrodes.
76. A unitary subcutaneous cardioverter-defibrillator according to
claim 74, further comprising: each of the sensing electrodes formed
in locations comprising at least one of a location between the pair
of electrodes and outside the pair of electrodes.
77. A unitary subcutaneous cardioverter-defibrillator according to
claim 74, further comprising: at least one such sensing electrode
formed non-circumferentially along an interior surface of the
biocompatible housing.
78. A unitary subcutaneous cardioverter-defibrillator according to
claim 69, wherein at least one surface of the biocompatible housing
forms a continuous radian curve.
79. A unitary subcutaneous cardioverter-defibrillator according to
claim 69, further comprising: a pulse generator integral to the
cardioversion-defibrillation circuitry and generating an
anti-arrhythmia biphasic waveform with characteristics comprising
at least one of a capacitance between approximately 50 .mu.F and
200 .mu.F, voltage between approximately 800 V and 2000 V, energy
between 40 J and 150 J, and a duration between approximately 5 msec
to 25 msec.
80. A unitary subcutaneous cardioverter-defibrillator according to
claim 69, further comprising: the cardioversion-defibrillation
circuitry comprising at least one of: monitoring circuitry deriving
physiological measures relating to at least one of QRS signal
morphology, QRS signal frequency content, QRS R-R interval
stability data, and QRS amplitude characteristics; a pulse
generator producing an anti-arrhythmia waveform for anti-arrhythmia
therapy via the pair of electrodes responsive to the
cardioversion-defibrillation circuitry; pacing circuitry
operatively conjunctive to the cardioversion-defibrillation
circuitry which generates at least one of an anti-bradycardia and
an anti-tachycardia pacing waveform via the pair of electrodes
responsive to the cardioversion-defibrillation circuitry; and
induction circuitry generating low amplitude voltage on a T-wave of
an ECG via the pair of electrodes responsive to the
cardioversion-defibrillation circuitry.
81. A unitary subcutaneous cardioverter-defibrillator according to
claim 69, wherein the biocompatible housing is constructed from at
least one of a titanium alloy and another biocompatible material,
such another material being malleable.
82. A unitary subcutaneous cardioverter-defibrillator with
electrically active canister for minimally invasive implantation,
comprising: a subcutaneously implantable canister comprising a
sterilizable biocompatible housing enclosing and containing
cardioversion-defibrillation circuitry interfaceable through the
biocompatible housing, the biocompatible housing formed into a
partially curved surface along a longitudinal axis; and a pair of
electrodes formed on opposite and facing ends of the biocompatible
housing and electrically interfaced via one or more internal
conductors to the cardioversion-defibrillation circuitry to deliver
an electrical therapy to the heart of a patient therebetween;
wherein a thicker end is defined on one end of the canister, said
thicker end being sized to contain the cardioversion-defibrillation
circuitry exclusive of the remainder of the canister.
83. A unitary subcutaneous cardioverter-defibrillator according to
claim 82 further comprising: self-contained power supply components
contained within the biocompatible housing and integral to the
cardioversion-defibrillation circuitry, consisting essentially of
four or more batteries and four or more capacitors and providing
power sufficient to generate the anti-arrhythmia biphasic
waveform.
84. A unitary subcutaneous cardioverter-defibrillator with
electrically active canister for minimally invasive implantation,
comprising: a subcutaneously implantable canister comprising a
sterilizable biocompatible housing enclosing and containing
cardioversion-defibrillation circuitry interfaceable through the
biocompatible housing, the biocompatible housing formed into a
partially curved surface along a longitudinal axis; and a pair of
electrodes formed on opposite and facing ends of the biocompatible
housing and electrically interfaced via one or more internal
conductors to the cardioversion-defibrillation circuitry to deliver
an electrical therapy to the heart of a patient therebetween;
further comprising: a removable core member containing the
operational circuitry separate from the biocompatible housing and
providing a plurality of electronic connectors; and the
biocompatible housing operationally disposed to receive the core
operational member via a plurality of matching electronic
connectors.
85. A unitary cardioversion-defibrillation device with electrically
conductive housing means for subcutaneous implantation, comprising:
means for housing and hermetically containing
cardioversion-defibrillation circuitry, the housing means defining
a curved and substantially electrically insulated outer surface,
with a downward taper continuously formed along an exterior
periphery of the housing means, and a pair of semi-converging
tapers continuously formed about opposite sides of the downward
taper; and means for delivering an electrical therapy from opposite
and facing ends of the housing means responsive to an autonomously
detected arrhythmic condition, the electrical therapy delivering
means being electrically connected via one or more internal
conductors to the cardioversion-defibrillation circuitry.
86. A unitary cardioversion-defibrillation device according to
claim 85, further comprising: means for monitoring and deriving
physiological measures relating to at least one of QRS signal
morphology, QRS signal frequency content, QRS R-R interval
stability data, and QRS amplitude characteristics; means for
producing an anti-arrhythmia waveform for anti-arrhythmia therapy
via the electrical therapy delivering means responsive to the
cardioversion-defibrillation circuitry; means for pacing circuitry
operatively conjunctive to the cardioversion-defibrillation
circuitry which generates at least one of an anti-bradycardia and
an anti-tachycardia pacing waveform via the electrical therapy
delivering means responsive to the cardioversion-defibrillation
circuitry; and means for induction circuitry generating low
amplitude voltage on a T-wave of an ECG via the electrical therapy
delivering means responsive to the cardioversion-defibrillation
circuitry.
87. A unitary cardioversion-defibrillation device according to
claim 85, further comprising: sensing means provided via the
electrical therapy delivering means, the sensing means being
electrically connected via the one or more internal conductors to
the cardioversion-defibrillation circuitry to interface with
sensing circuitry.
88. A unitary cardioversion-defibrillation device according to
claim 85, further comprising: sensing means provided abutting and
electrically insulated from the housing means, the sensing means
being electrically connected via the one or more internal
conductors to the cardioversion-defibrillation circuitry to
interface with sensing circuitry.
89. A subcutaneous cardioverter-defibrillator according to claim
88, further comprising: each of the sensing means formed in
locations comprising at least one of a location between the
electrical therapy delivering means and outside the electrical
therapy delivering means.
90. A unitary cardioversion-defibrillation device according to
claim 85, further comprising: at least one electrically insulated
surface defined about a surface of the housing means facing the
heart and juxtaposed to the electrical therapy delivering
means.
91. A unitary cardioversion-defibrillation device according to
claim 85, further comprising: pulse generating means integral to
the cardioversion-defibrillation circuitry and generating an
anti-arrhythmia biphasic waveform with characteristics comprising
at least one of a capacitance between approximately 50 .mu.F and
200 .mu.F, voltage between approximately 800 V and 2000 V, energy
between 40 J and 150 J, and a duration between approximately 5 msec
to 25 msec.
92. A unitary cardioversion-defibrillation device according to
claim 85, further comprising: a radian bend continuously formed
approximately axial to the housing means.
93. A unitary cardioversion-defibrillation device according to
claim 85, further comprising: operational means containing the
cardioversion-defibrillation circuitry separate from the housing
means and providing-means for connecting along a proximal end; and
receiving means formed within a distal end of the housing means
operationally disposed to receive the operational means via the
connecting means.
94. A unitary cardioversion-defibrillation device according to
claim 85, wherein the housing means is constructed from at least
one of a titanium alloy and another biocompatible material, such
another material being malleable.
95. An implantable unitary subcutaneous cardioverter-defibrillator
with electrically active canister, comprising: an implantable
canister providing a curved housing enclosing and containing
cardioversion-defibrillation circuitry; a pair of electrodes formed
on opposite and facing ends of the housing and electrically
interfaced via one or more conductors to the
cardioversion-defibrillation circuitry to deliver an electrical
therapy to the heart of a patient responsive to an autonomously
detected arrhythmic condition; and a removable core operational
member containing the cardioversion-defibrillation circuitry
separate and interchangeably from the housing and providing a
plurality of connectors, the housing being operationally disposed
to receive the core operational member via a plurality of matching
connectors.
96. An implantable unitary subcutaneous cardioverter-defibrillator
according to claim 95, further comprising: an electrically
insulated surface juxtaposed to the pair of electrodes and
substantially interposed therefrom by an electrically insulated
area.
97. An implantable unitary subcutaneous cardioverter-defibrillator
according to claim 95, further comprising: a plurality of sensing
electrodes formed on the housing and electrically connected with
the one or more conductors to the cardioversion-defibrillation
circuitry, each of the sensing electrodes interfacing with sensing
circuitry within the cardioversion-defibrillation circuitry and
providing a sensing function.
98. An implantable unitary subcutaneous cardioverter-defibrillator
according to claim 97, further comprising: each of the sensing
electrodes formed on locations along the, housing comprising at
least one of a surface of the implantable canister facing the heart
and a surface of the implantable canister facing toward the
skin.
99. An implantable unitary subcutaneous cardioverter-defibrillator
according to claim 95, further comprising: an anti-arrhythmic pulse
generator integral to the cardioversion-defibrillation circuitry
and generating an anti-arrhythmia biphasic waveform between the
pair of electrodes with characteristics comprising at least one of
a capacitance between approximately 50 .mu.F and 200 .mu.F, voltage
between approximately 800 V and 2000 V, energy between 40 J and 150
J, and a duration between approximately 5 msec to 25 msec.
100. An implantable unitary subcutaneous cardioverter-defibrillator
with electrically active canister, comprising: an implantable
canister providing a curved housing enclosing and containing
cardioversion-defibrillation circuitry; a pair of electrodes formed
on opposite and facing ends of the housing and electrically
interfaced via one or more conductors to the
cardioversion-defibrillator circuitry to deliver an electrical
therapy to the heart of a patient responsive to an autonomously
detected arrhythmic condition; a removable core operational member
containing the cardioversion-defibrillation circuitry separate and
interchangeably from the housing and providing a plurality of
connectors, the housing operationally disposed to receive the core
operational member via a plurality of matching connectors.
101. A method for providing anti-arrhythmia therapy via a unitary
subcutaneous cardioverter-defibrillator, comprising: implanting a
canister comprising a curved biocompatible housing subcutaneously
in a patient in the anterior thorax approximately level with the
inframammary crease and extending posteriorly towards the left
posterior axillary line, the biocompatible housing enclosing and
containing cardioversion-defibrillation circuitry and defining a
pair of electrodes on the outer surface of the biocompatible
housing that faces the heart and electrically connected to the
cardioversion-defibrillation circuitry; and delivering an
electrical therapy comprising an anti-arrhythmia waveform to the
heart of a patient from the pair of electrodes.
102. A method according to claim 101, the method further
comprising: implanting the canister in a region proximate to at
least one of the fourth, fifth and sixth anterior rib spaces of a
patient.
103. A method according to claim 101, the method further
comprising: providing a plurality of sensing electrodes formed on
the canister, electrically isolated from the pair of electrodes,
each sensing electrode interfacing with sensing circuitry to the
cardioversion-defibrillation circuitry; and monitoring and deriving
cardiac physiological measures relating to at least one of QRS
signal morphology, QRS signal frequency content, QRS R-R interval
stability data, and QRS amplitude characteristics via the sensing
electrodes.
104. A method according to claim 101, further comprising:
generating low amplitude voltage on a T-wave of an ECG via the pair
of electrodes responsive to the cardioversion-defibrillation
circuitry.
Description
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for
performing electrical cardioversion/defibrillation and optional
pacing of the heart via a totally subcutaneous non-transvenous
system.
BACKGROUND OF THE INVENTION
Defibrillation/cardioversion is a technique employed to counter
arrhythmic heart conditions including some tachycardias in the
atria and/or ventricles. Typically, electrodes are employed to
stimulate the heart with electrical impulses or shocks, of a
magnitude substantially greater than pulses used in cardiac
pacing.
Defibrillation/cardioversion systems include body implantable
electrodes and are referred to as implantable
cardioverter/defibrillators (ICDs). Such electrodes can be in the
form of patches applied directly to epicardial tissue, or at the
distal end regions of intravascular catheters, inserted into a
selected cardiac chamber. U.S. Pat. Nos. 4,603,705, 4,693,253,
4,944,300, 5,105,810, the disclosures of which are all incorporated
herein by reference, disclose intravascular or transvenous
electrodes, employed either alone or in combination with an
epicardial patch electrode. Compliant epicardial defibrillator
electrodes are disclosed in U.S. Pat. Nos. 4,567,900 and 5,618,287,
the disclosures of which are incorporated herein by reference. A
sensing epicardial electrode configuration is disclosed in U.S.
Pat. No. 5,476,503, the disclosure of which is incorporated herein
by reference.
In addition to epicardial and transvenous electrodes, subcutaneous
electrode systems have also been developed. For example, U.S. Pat.
Nos. 5,342,407 and 5,603,732, the disclosures of which are
incorporated herein by reference, teach the use of a pulse
monitor/generator surgically implanted into the abdomen and
subcutaneous electrodes implanted in the thorax. This system is far
more complicated to use than current ICD systems using transvenous
lead systems together with an active can electrode and therefore it
has no practical use. It has in fact never been used because of the
surgical difficulty of applying such a device (3 incisions), the
impractical abdominal location of the generator and the
electrically poor sensing and defibrillation aspects of such a
system.
Recent efforts to improve the efficiency of ICDs have led
mnanufacturers to produce ICDs which are small enough to be
implanted in the pectoral region. In addition, advances in circuit
design have enabled the housing of the ICD to form a subcutaneous
electrode. Some examples of ICDs in which the housing of the ICD
serves as an optional additional electrode are described in U.S.
Pat. Nos. 5,133,353, 5,261,400, 5,620,477, and 5,658,321, the
disclosures of which are incorporated herein by reference.
ICDs are now an established therapy for the management of life
threatening cardiac rhythm disorders, primarily ventricular
fibrillation (V-Fib). ICDs are very effective at treating V-Fib,
but are therapies that still require significant surgery.
As ICD therapy becomes more prophylactic in nature and used in
progressively less ill individuals, the requirement of ICD therapy
to use intravenous catheters and transvenous leads is an impediment
to very long term management as most individuals will begin to
develop complications related to lead system malfunction sometime
in the 5-10 year time frame, often earlier. In addition, chronic
transvenous lead systems, their reimplantation and removals, can
damage major cardiovascular venous systems and the tricuspid valve,
as well as result in life threatening perforations of the great
vessels and heart. Consequently, use of transvenous lead systems,
despite their many advantages, are not without their chronic
patient management limitations in those with life expectancies of
>5 years. Moreover, transvenous ICD systems also increase cost
and require specialized interventional rooms and equipment as well
as special skill for insertion. These systems are typically
implanted by cardiac electrophysiologists who have had a great deal
of extra training.
In addition to the background related to ICD therapy, the present
invention requires a brief understanding of automatic external
defibrillator (AED) therapy. AEDs employ the use of cutaneous patch
electrodes to effect defibrillation under the direction of a
bystander user who treats the patient suffering from V-Fib. AEDs
can be as effective as an ICD if applied to the victim promptly
within 2 to 3 minutes.
AED therapy has great appeal as a tool for diminishing the risk of
death in public venues such as in air flight. However, an AED must
be used by another individual, not the person suffering from the
potentially fatal rhythm. It is more of a public health tool than a
patient-specific tool like an ICD. Because >75% of cardiac
arrests occur in the home, and over half occur in the bedroom,
patients at risk of cardiac arrest are often alone or asleep and
can not be helped in time with an AED. Moreover, its success
depends to a reasonable degree on an acceptable level of skill and
calm by the bystander user.
What is needed therefore, is a combination of the two forms of
therapy which would provide prompt and near-certain defibrillation,
like an ICD, but without the long-term adverse sequelae of a
transvenous lead system while simultaneously using most of the
simpler and lower cost technology of an AED. What is also needed is
a cardioverter/defibrillator that is of simple design and can be
comfortably implanted in a patient for many years. We call such a
device a unitary sub-cutaneous only ICD (US-ICD) and is described
in detail below.
SUMMARY OF THE INVENTION
The preferred embodiment for the unitary subcutaneous only ICD
(US-ICD) with optional pacing consists of five basic components: 1)
a curved housing which houses a battery supply, capacitor, and
operational circuitry; 2) two cardioversion/defibrillating
electrodes are attached to the outer surface of the housing; 3) one
or more sensing electrodes located on the housing; and 4) sense
circuitry suitable to an ICD or AED V-FIB detection algorithm.
Additionally, an application system is provided for simple
insertion of the US-ICD. No transvenous lead system is used,
eliminating a significant impediment to broader scale prophylactic
use.
The housing will provide energy and voltage intermediate to that
available with ICD and AEDs. The typical maximum voltage necessary
for ICDs using most biphasic waveforms is approximately 750 V and
associated maximum energy of approximately 40 J. The typical
maximum voltage necessary for AEDs is approximately 2000-5000 V
with an associated maximum energy of approximately 150-360 J. The
US-ICD of the present invention will use voltages in the range of
800 to 2000 V and associated with energies of approximately 40-150
J.
The cardioversion/defibrillation electrodes are electrically
insulated from each other and are about 5-10 cm length. In the
preferred embodiment, the sense electrodes are located between the
cardioversion/defibrillation electrodes and are spaced about 4 cm
from each other to provide a reasonable QRS signal from a
subcutaneous extracardiac sampling location but may be of variable
length to allow for sense optimization.
The sense circuitry in the preferred embodiment is designed to be
highly sensitive and specific to the presence or absence of life
threatening ventricular arrhythmias only. Features of the detection
algorithm are programmable but the algorithm is focused on the
detection of V-Fib and high rate ventricular tachycardia (V-Tach)
of greater than 240 bpm. This type of cardioverter-defibrillator is
not necessarily designed to replace ICD therapy for those with
pre-identified problems of V-Tach/V-Fib or even atrial
fibrillation, but is particularly geared to use as a prophylactic,
long-term device, used for the life of the patient at risk of
his/her first V-Fib/V-Tach event. The device of the present
invention may infrequently be used for an actual life threatening
event but can be employed in large populations of individuals at
modest risk and with modest cost by physicians of limited
experience. Consequently, the preferred embodiment of the present
invention focuses only on the detection and therapy of the most
malignant rhythm disorders. As part of the detection algorithm's
applicability to children, the upper rate range is programmable
upward for use in children, who are known to have more rapid
supraventricular tachycardias as well as more rapid ventricular
tachycardias compared to adults.
The incision to apply the device of the present invention can be
anywhere on the thorax although in the preferred embodiment, the
device of the present invention will be applied in the anterior
mid-clavicular line approximately at the level of the mammary
crease beneath the left areolus. A subcutaneous path will then be
made and will extend to the posterior thoracic region ideally at
the level of the inferior scapula tip. Such a lead position will
allow for a good transthoracic current delivery vector as well as
positioning of the proximally positioned sense bipole in a good
location for identification of the QRS ECG signal. A specially
designed curved introducer set, through which local anesthetic can
be delivered, is provided to assist in the placement of the
US-ICD.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention, reference is now made
to the drawings where like numerals represent similar objects
throughout the figures where:
FIG. 1 is a schematic view of a Unitary Subcutaneous ICD (US-ICD)
of the present invention;
FIG. 2 is a schematic view of the US-ICD subcutaneously implanted
in the thorax of a patient;
FIG. 3 is a schematic view of the method of making a subcutaneous
path from the preferred incision for implanting the US-ICD.
FIG. 4 is a schematic view of an introducer for performing the
method of US-ICD implantation; and
FIG. 5 is an exploded schematic view of an alternate embodiment of
the present invention with a plug-in portion that contains
operational circuitry and means for generating
cardioversion/defibrillation shock waves.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to FIG. 1, the US-ICD of the present invention is
illustrated. The US-ICD consists of a curved housing 11 with a
first and second end. The first end 13 is thicker than the second
end 15. This thicker area houses a battery supply, capacitor and
operational circuitry for the US-ICD. The circuitry will be able to
monitor cardiac rhythms for tachycardia and fibrillation, and if
detected, will initiate charging the capacitor and then delivering
cardioversion/defibrillation energy through the two
cardioversion/defibrillating electrodes 17 and 19 located on the
outer surface of the two ends of the housing. Examples of such
circuitry are described in U.S. Pat. Nos. 4,693,253 and 5,105,810,
the entire disclosures of which are herein incorporated by
reference. The circuitry can provide cardioversion/defibrillation
energy in different types of wave forms. In the preferred
embodiment, a 100 uF biphasic wave form is used of approximately
10-20 ms total duration and with the initial phase containing
approximately 2/3 of the energy, however, any type of wave form can
be utilized such as monophasic, biphasic, multiphasic or
alternative waveforms as is known in the art.
In addition to providing cardioversion/defibrillation energy, the
circuitry can also provide transthoracic cardiac pacing energy. The
optional circuitry will be able to monitor the heart for
bradycardia and/or tachycardia rhythms. Once a bradycardia or
tachycardia rhythm is detected, the circuitry can then deliver
appropriate pacing energy at appropriate intervals through the
electrodes. Pacing stimuli will be biphasic in the preferred
embodiment and similar in pulse amplitude to that used for
conventional transthoracic pacing.
This same circuitry can also be used to deliver low amplitude
shocks on the T-wave for induction of ventricular fibrillation for
testing S-ICD performance in treating V-Fib as is described in U.S.
Pat. No. 5,129,392, the entire disclosure of which is hereby
incorporated by reference. Also the circuitry can be provided with
rapid induction of ventricular fibrillation or ventricular
tachycardia using rapid ventricular pacing. Another optional way
for inducing ventricular fibrillation would be to provide a
continuous low voltage, i.e. about 3 volts, across the heart during
the entire cardiac cycle.
Another optional aspect of the present invention is that the
operational circuitry can detect the presence of atrial
fibrillation as described in Olson, W. et al. "Onset And Stability
For Ventricular Tachyarrhythmia Detection in an Implantable
Cardioverter and Defibrillator, Computers in Cardiology (1986) pp
167-170. Detection can be provided via R-R Cycle length instability
detection algorithms. Once atrial fibrillation has been detected,
the operational circuitry will then provide QRS synchronized atrial
defibrillation/cardioversion using the same shock energy and
waveshape characteristics used for ventricular
defibrillation/cardioversion.
The sensing circuitry will utilize the electronic signals generated
from the heart and will primarily detect QRS waves. In one
embodiment, the circuitry will be programmed to detect only
ventricular tachycardias or fibrillations. The detection circuitry
will utilize in its most direct form, a rate detection algorithm
that triggers charging of the capacitor once the ventricular rate
exceeds some predetermined level for a fixed period of time: for
example, if the ventricular rate exceeds 240 bpm on average for
more than 4 seconds. Once the capacitor is charged, a confirmatory
rhythm check would ensure that the rate persists for at least
another 1 second before discharge. Similarly, termination
algorithms could be instituted that ensure that a rhythm less than
240 bpm persisting for at least 4 seconds before the capacitor
charge is drained to an internal resistor. Detection, confirmation
and termination algorithms as are described above and in the art
can be modulated to increase sensitivity and specificity by
examining QRS beat-to-beat uniformity, QRS signal frequency
content, R-R interval stability data, and signal amplitude
characteristics all or part of which can be used to increase or
decrease both sensitivity and specificity of S-ICD arrhythmia
detection function.
In addition to use of the sense circuitry for detection of V-Fib or
V-Tach by examining the QRS waves, the sense circuitry can check
for the presence or the absence of respiration. The respiration
rate can be detected by monitoring the impedance across the thorax
using subthreshold currents delivered across the active can and the
high voltage subcutaneous lead electrode and monitoring the
frequency in undulation in the waveform that results from the
undulations of transthoracic impedence during the respiratory
cycle. If there is no undulation, then the patient is not respiring
and this lack of respiration can be used to confirm the QRS
findings of cardiac arrest. The same technique can be used to
provide information about the respiratory rate or estimate cardiac
output as described in U.S. Pat. Nos. 6,095,987, 5,423,326,
4,450,527, the entire disclosures of which are incorporated herein
by reference.
The housing of the present invention can be made out of titanium
alloy or other presently preferred ICD designs. It is contemplated
that the housing is also made out of biocompatible plastic
materials that electronically insulate the electrodes from each
other. However, it is contemplated that a malleable canister that
can conform to the curvature of the patient's chest will be
preferred. In this way the patient can have a comfortable canister
that conforms to the unique shape of the patient's rib cage.
Examples of conforming ICD housings are provided in U.S. Pat. No.
5,645,586, the entire disclosure of which is herein incorporated by
reference. In the preferred embodiment, the housing is curved in
the shape of a 5.sup.th rib of a person. Because there are many
different sizes of people, the housing will come in different
incremental sizes to allow a good match between the size of the rib
cage and the size of the US-ICD. The length of the US-ICD will
range from about 15 to about 50 cm. Because of the primary
preventative role of the therapy and the need to reach energies
over 40 Joules, a feature of the preferred embodiment is that the
charge time for the therapy, intentionally be relatively long to
allow capacitor charging within the limitations of device size.
The thick end of the housing is currently needed to allow for the
placement of the battery supply, operational circuitry, and
capacitors. It is contemplated that the thick end will be about 0.5
cm to about 2 cm wide with about 1 cm being presently preferred. As
microtechnology advances, the thickness of the housing will become
smaller. Examples of small ICD housings are disclosed in U.S. Pat.
Nos. 5,957,956 and 5,405,363, the entire disclosures of which are
herein incorporated by reference.
The two cardioversion/defibrillation electrodes on the housing are
used for delivering the high voltage cardioversion/defibrillation
energy across the heart. In the preferred embodiment, the
cardioversion/defibrillation electrodes are coil electrodes,
however, other cardioversion/defibrillation electrodes could be
used such as having electrically isolated active surfaces or
platinum alloy electrodes. The coil cardioversion/defibrillation
electrodes are about 5-10 cm in length. Located on the housing
between the two cardioversion/defibrillation electrodes are two
sense electrodes 25 and 27. The sense electrodes are spaced far
enough apart to be able to have good QRS detection. This spacing
can range from 1 to 10 cm with 4 cm being presently preferred. The
electrodes may or may not be circumferential with the preferred
embodiment. Having the electrodes non-circumferential and
positioned outward, toward the skin surface, is a means to minimize
muscle artifact and enhance QRS signal quality. The sensing
electrodes are electrically isolated from the
cardioversion/defibrillation electrode via insulating areas 23.
Analogous types of cardioversion/defibrillation electrodes are
currently commercially available in a transvenous configuration.
For example, U.S. Pat. No. 5,534,022, the entire disclosure of
which is herein incorporated by reference, discloses a composite
electrode with a coil cardioversion/defibrillation electrode and
sense electrodes. Modifications to this arrangement are
contemplated within the scope of the invention. One such
modification is to have the sense electrodes at the two ends of the
housing and have the cardioversion/defibrillation electrodes
located in between the sense electrodes. Another modification is to
have three or more sense electrodes spaced throughout the housing
and allow for the selection of the two best sensing electrodes. If
three or more sensing electrodes are used, then the ability to
change which electrodes are used for sensing would be a
programmable feature of the US-ICD to adapt to changes in the
patient physiology and size over time. The programming could be
done via the use of physical switches on the canister, or as
presently preferred, via the use of a programming wand or via a
wireless connection to program the circuitry within the
canister.
The housing will provide energy and voltage intermediate to that
available with ICDs and most AEDs. The typical maximum voltage
necessary for ICDs using most biphasic waveforms is approximately
750 Volts with an associated maximum energy of approximately 40
Joules. The typical maximum voltage necessary for AEDs is
approximately 2000-5000 Volts with an associated maximum energy of
approximately 200-360 Joules depending upon the model and waveform
used. The US-ICD of the present invention uses maximum voltages in
the range of about 800 to about 2000 Volts and is associated with
energies of about 40 to about 150 Joules. The capacitance of the
S-ICD could range from about 50 to about 200 micro farads.
The sense circuitry contained within the housing is highly
sensitive and specific for the presence or absence of life
threatening ventricular arrhythmias. Features of the detection
algorithm are programmable and the algorithm is focused on the
detection of V-FIB and high rate V-TACH (>240 bpm). Although the
US-ICD of the present invention may rarely be used for an actual
life threatening event, the simplicity of design and implementation
allows it to be employed in large populations of patients at modest
risk with modest cost by non-cardiac electrophysiologists.
Consequently, the US-ICD of the present invention focuses mostly on
the detection and therapy of the most malignant rhythm disorders.
As part of the detection algorithm's applicability to varying
patient populations, the detection rate range is programmable
upward or downward to meet the needs of the particular patient
based on their cardiac condition and age.
Turning now to FIG. 2, the optimal subcutaneous placement of the
US-ICD of the present invention is illustrated. As would be evident
to a person skilled in the art, the actual location of the US-ICD
is in a subcutaneous space that is developed during the
implantation process. The heart is not exposed during this process
and the heart is schematically illustrated in the figures only for
help in understanding where the device and its various electrodes
are three dimensionally located in the thorax of the patient. The
US-ICD is located between the left mid-clavicular line
approximately at the level of the inframammary crease at
approximately the 5.sup.th rib and the posterior axillary line,
ideally just lateral to the left scapula. This way the US-ICD
provides a reasonably good pathway for current delivery to the
majority of the ventricular myocardium.
FIG. 3 schematically illustrates the method for implanting the
US-ICD of the present invention. An incision 31 is made in the left
anterior axillary line approximately at the level of the cardiac
apex. A subcutaneous pathway 33 is then created that extends
posteriorly to allow placement of the US-ICD. The incision can be
anywhere on the thorax deemed reasonable by the implanting
physician although in the preferred embodiment, the US-ICD of the
present invention will be applied in this region. The subcutaneous
pathway 33 is created medially to the inframammary crease and
extends posteriorly to the left posterior axillary line. The
pathway is developed with a specially designed curved introducer 40
(see FIG. 4). The trocar has a proximal handle 41 and a curved
shaft 43. The distal end 45 of the trocar is tapered to allow for
dissection of the subcutaneous pathway 33 in the patient.
Preferably, the trocar is cannulated having a central lumen 46 and
terminating in an opening 48 at the distal end. Local anesthetic
such as lidocaine can be delivered, if necessary, through the lumen
or though a curved and elongated needle designed to anesthetize the
path to be used for trocar insertion should general anesthesia not
be employed. Once the subcutaneous pathway is developed, the US-ICD
is implanted in the subcutaneous space, the skin incision is closed
using standard techniques.
As described previously, the US-ICDs of the present invention vary
in length and curvature. The US-ICDs are provided in incremental
sizes for subcutaneous implantation in different sized patients.
Turning now to FIG. 5, a different embodiment is schematically
illustrated in exploded view which provides different sized US-ICDs
that are easier to manufacture. The different sized US-ICDs will
all have the same sized and shaped thick end 13. The thick end is
hollow inside allowing for the insertion of a core operational
member 53. The core member comprises a housing 57 which contains
the battery supply, capacitor and operational circuitry for the
US-ICD. The proximal end of the core member has a plurality of
electronic plug connectors. Plug connectors 61 and 63 are
electronically connected to the sense electrodes via pressure fit
connectors (not illustrated) inside the thick end which are
standard in the art. Plug connectors 65 and 67 are also
electronically connected to the cardioverter/defibrillator
electrodes via pressure fit connectors inside the thick end. The
distal end of the core member comprises an end cap 55, and a ribbed
fitting 59 which creates a water-tight seal when the core member is
inserted into opening 51 of the thick end of the US-ICD.
The core member of the different sized and shaped US-ICD will all
be the same size and shape. That way, during an implantation
procedures, multiple sized US-ICDs can be available for
implantation, each one without a core member. Once the implantation
procedure is being performed, then the correct sized US-ICD can be
selected and the core member can be inserted into the US-ICD and
then programmed as described above. Another advantage of this
configuration is when the battery within the core member needs
replacing it can be done without removing the entire US-ICD.
The US-ICD device and method of the present invention may be
embodied in other specific forms without departing from the
teachings or essential characteristics of the invention. The
described embodiments are therefore to be considered in all
respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are therefore to be
embraced therein.
* * * * *